Compelling evidence exists that the adult brain can be modified by sensory experiences. Understanding experience-dependent plasticity has implications for clinical remediation strategies in neurological and auditory disorders. In this proposal, I will use a well-established and powerful plasticity paradigm to study how sensory experience alters receptive field size, maximum following rate, and fidelity of cortical representations, from neurons in the primary auditory cortex. To accomplish these objectives, I will pair tones, rapidly modulated trains of noise bursts, and complex speech stimuli with activation of the cholinergic nucleus basalis, located in the basal forebrain, and examine how sensory input guides cortical plasticity. After sensory experience with each of these three classes of stimuli, I will then collect dense cortical maps and determine how these sounds contribute to different forms of plasticity in each group. The experiments in this proposal will extend our knowledge of basic principles of auditory cortical plasticity to include complex spatiotemporal stimuli. It is my hypothesis that differential sensory experience will shape cortical representations in a systematic and quantifiable manner.